Another book to look at is "Misdiagnosis and Dual Diagnoses of Gifted Children" by Dr. James Webb. Very interesting read; I actually got it because I suspected my HG+ ds6 might have ADD (no H for him). It didn't put my suspicions to rest, but it did give me more to think about.
Have you tried behavior therapy in lieu of or in conjunction with meds? I've read that diet changes (fewer carbs, more protein) and behavior modification strategies can work wonders with kids who are borderline, and with my own ds, we definitely see an improvement with a high-protein diet.
You may want to re-do the IQ testing with a tester experienced with gifted kids and see what he thinks. Worth looking into, at least ...
Good luck!
